The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named co-inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
With present day cars and trucks that utilize an internal combustion engine, the engine has an engine block with a block valve. The block valve operates to control the flow of coolant through the block. Routine city driving conditions, however, typically do not require a flow of engine coolant through the engine block. In other words, a stagnant amount of coolant in the engine block is sufficient to help maintain the engine block temperature within an acceptable range and below the temperature at which coolant boiling will start to occur. However, stagnant coolant generally does not provide accurate temperature information when being sensed with a temperature sensor that requires a degree of flow of the coolant over its sensing element. In other words, the stagnant coolant, because it is not flowing, will not enable the temperature sensor to produce accurate temperature readings for the stagnant coolant in the engine block. So if an unpredictable condition was to arise, for example steamer hole plugging, this condition would not be easy to detect from a system that only gauges the engine block temperature with an open loop determination.
It is also highly desirable to maintain the engine block at the highest temperature possible without causing boiling of the coolant within the cooling jackets formed within the engine block. Maintaining the engine block at the highest allowable temperature without producing coolant boiling can enhance fuel efficiency by helping to reduce friction of the moving parts within the engine and maintain the engine oil at an optimum temperature. Therefore, a challenge exists in accurately gauging the engine block temperature during low load operation (e.g., city driving), while still providing the ability to monitor, in a closed loop fashion, thermal conductance and thermal radiation information, and to further control the coolant flow under both low load and high load engine operation while maximizing the thermal energy within the engine block without allowing a coolant boiling condition in the block to arise.